Infrared instruments (e.g., detectors, cameras, spectrometers, hyperspectral imagers, etc.) require black absorptive coatings on internal surfaces to trap scattered and stray photons in order to achieve better results. This black absorptive coating is typically accomplished by applying any one of a number of black paints. Although paints are inexpensive and simple to apply, they have several disadvantages. Paints can be fragile and difficult to clean. When subjected to temperature extremes, hot and/or cold, they can flake or shed particles. Also, uniform application may be difficult on small assemblies. And most importantly in many contexts, black paints have poor vacuum performance, and require prolonged baking to reduce outgassing.
Most high performance infrared detectors operate at cryogenic temperatures and hence must be installed in a vacuum dewar to prevent condensation and to reduce the heat load to a manageable level. For laboratory applications, the vacuum is typically supplied by a mechanical pump. For field applications and especially on mobile platforms this method of supplying a vacuum is not practical. Instead, field dewars are sealed off and incorporate getter pumps (e.g., Ion Getter Pumps) of limited capacity to maintain the vacuum.
Therefore, an absorptive coating that limits or eliminates some or all of the problems associated with black paints would be very beneficial to applications using infrared instruments.